San Francisco takes a bit of a beating in the new big-screen version of 'Godzilla.' (AP Photo/Warner Bros. Pictures) (Warner Bros. Pictures)

“History shows again and again how nature points out the folly of maaa-aann …”

Blue Oyster Cult nailed it in their 1977 ode to our favorite big green lizard, Godzilla. Since he first waded ashore in 1954, and through about 30 films since, he has stood as the ultimate metaphor for the danger of nuclear weapons, a raging sentinel dispatched from the deep by a distressed Mother Nature bent on spanking humankind for its hubris in daring to split the atom.

The new 3-D update of the legend stays true to its nuclear-powered origins (and even throws in a sheen of concern about global climate change, though these precise words are never uttered).

The opening sequence sets the right ominous tone, with grainy footage of post-World War II nuclear tests in the Pacific that supposedly were a cover for U.S. military efforts to kill Godzilla.

But it doesn’t take long for a sinking feeling to set in. Warner Bros. may have thought hiring relative rookies to helm this mega-budget summer extravaganza might inject a shot of fresh, new blood into what is admittedly a pretty hoary concept. But all director Gareth Edwards and writers Max Borenstein and Dave Callaham show is that they’re, well, relative rookies.

The biggest sin: A full hour of human-centric silliness elapses before we get our first full view of Godzilla. This rendition of the big guy is fabulous, and when he lets loose one of those full-throated roars, it’s a hair-raising, giggle-inducing hoot. But then he vanishes again for most of another hour as the script resumes its focus on human characters that no viewers will care about.

The first few sequences at least benefit from the presence of Bryan Cranston, fresh off his run in “Breaking Bad,” who doesn’t just chew scenery; he mauls it.

The story opens in the Philippines in 1999, where two scientists, Ken Watanabe (this film’s Japanese ambassador) and Sally Hawkins, find huge, misshapen fossils in an underground cavern uncovered by a mining company.

In Japan, meanwhile, Cranston is an engineer at a nuclear plant being rocked by tremors. Everyone thinks it’s earthquakes, but after the plant has a meltdown and his wife (Juliette Binoche) dies in the mayhem, Cranston thinks something else is to blame.

Jump forward 15 years. Cranston’s son (Aaron Taylor-Johnson) is a Navy lieutenant with a wife (Elizabeth Olsen) and young son. Cranston is still in Japan, a half-crazed hermit trying to unravel the mystery of the plant disaster.

The lengthy setup grows tedious, especially after Cranston drops out of the picture. Taylor-Johnson is good-looking but bland, and he can’t quite carry leading-man weight.

All the preamble hooey leads to the release of two mammoth insectoid creatures dubbed MUTOs (that’s Massive Unidentified Terrestrial Organisms to you) that feed on nuclear radiation — one male, one female, both bent on hatching a large brood of baby MUTOs.

Godzilla’s entry into the fray is hopelessly muddled. As best I could tell, the long-dormant beast awakes after sensing the presence of the MUTOs and is spurred to track and attack them out of an instinctual imperative to reign as the world’s ultimate “alpha predator.” Not for nuthin’ is the big guy known as the “king of all monsters.”

The trail eventually tracks across the Pacific to Hawaii, then toward the California coast, opening the door for the U.S. Navy to take center stage, led by a buzz-cut, silver-haired admiral (David Straithairn).

The Marine Corps declined to participate after seeing this script, and it’s not hard to guess why. I lost track of the number of times swabbies fire small-caliber weapons at Godzilla and/or the MUTOs, as if bullets will hurt 350-foot armor-plated beasts.

Similarly, Navy warships shadow Godzilla across the Pacific — like a hundred yards off his fat haunches. So every time he dives or surfaces, warships get tossed around like toys in a bathtub. Standoff aerial recon, anyone?

Ah, well. It’s pointless to highlight the abundant absurdities; the tweens and teens to whom such films are aimed won’t care. But there’s no disputing that this flick suffers from the most common malady of its genre: An overcooked and unengaging human element that feels like endless filler delaying the main event.

Eventually, mercifully, that does arrive, as Godzilla squares off against the MUTOs in a heart-stopping, jaw-dropping spectacle; when the plates on Godzilla’s back start to glow and he belts out a blast of crystal-blue “atomic breath,” the theater walls shake. (Although the film makes curiously negligible use of 3-D effects in this climactic scene, lending more weight to the argument that many films are made in 3-D mainly to tack a few more bucks onto already sky-high octoplex ticket prices.)

However, be advised that this mind-blowing sequence comprises only the final 15 minutes of a 135-minute movie — and those first 120 minutes are mostly a long, tough slog.